Machines are typically controlled by a combination of control devices. For example, an operator may use one device to move the machine into a desired direction, for example, a steering wheel or yolk, a different device to accelerate and decelerate the machine, for example, joystick, pedals or levers, and another device, for example, a joystick, to operate an implement of the machine, such as a bucket or shovel.
Currently, machines such as skid steer loaders, excavators, cranes, wheel loaders, and the like, use joystick-type control devices to control the motion of their implements or the speed of the machine. These joysticks may have two, three or more degrees of freedom of motion, each of which corresponds to a particular direction or type of motion of the machine or work implement. When an operator is manipulating the control, the operator can move the control in various fashions to achieve the desired movement of the machine, placement and trajectory of the work implement, and the like.
During some operations of a machine, vibrations may be perceptible in the operator cab, and specifically, in the handle of a joystick or other manual control device. Such vibrations may be the result of travel of the machine over uneven terrain, vibration of a work implement that is transferred to the cab and other vibration sources. Examples of work implements that can induce a vibration include, but are not limited to, pneumatic hammers, augers, and the like. Vibrations/oscillations, whether produced by the machine, or the implement, or otherwise are generally known as Operator Induced Oscillation (OIO) when the vibration (motion) of the machine, implement, or the like, causes motion of the operator during operation of the machine, which causes unwanted motion of the input device (joystick, lever, pedal, and the like.)
U.S. Pat. No. 4,298,833 issued Nov. 3, 1981 (the '833 patent) discloses an apparatus for damping operator induced oscillations of a controlled system responding to an operator controller signal utilizing a lag-lead filter for frequency and amplitude estimation of the control input, and a rectification and smoothing filter for producing a signal proportional to the absolute value of the frequency and amplitude estimate for use in suppression of the control system output signal. In one embodiment this is accomplished by computing a correction signal in a correction generating section. In a second embodiment, a second rectification and smoothing filter produces a signal proportional to the absolute value of the controlled input signal. A ratio of the outputs of the first and second rectification and smoothing filters is then used in a generator to generate a gain factor for the control system to reduce the gain of the output signal of the control system. This type of system has drawbacks. It does not use the filtered output to adjust the physical resistance of the manual control input device used by an operator to control a machine or implement. A better system for the operator is needed.